The present invention relates to a data transmission method and a data transmission apparatus which carry out data processing through a data bus.
In the case when a CPU carries out a data transmission process through a 32-bit bus, for example, upon carrying out audio data send/receive processes, when the audio data has a 16-bit width, reading and writing operations are carried out on higher-order and lower-order half words in a 32-bit register for every two data. When the data has a bit width of 18, 20, 24 or the like, reading and writing operations are carried out on a higher-order or lower-order bit in a 32-bit register for each data.
However, in the case of data having the bit width of 18, 20, 24 or the like, data in the higher-order or lower-order remaining bits (14, 12, 8 bit) is nullified. For this reason, the efficiency of use of a data bus interface used by the CPU is deteriorated. Moreover, since the CPU carries out encode/decode processes or the like on audio data, the efficiency of use of a memory for storing audio data is also deteriorated.
In the future, the CPU comes to carry out multi-media processes, such as audio, image and data processings, in portable terminals, digital cameras and the like. In these cases, one bus is shared by a number of interfaces so that it becomes essential to improve the efficiency of use of the bus.